Re: Alternator vs Dynamo

The major advantage of an alternator over a dynamo is that it is a three phase unit as compared to a single phase unit. In simple terms, alternator will give a much higher charge rate at slow speeds (idle) since on one rotation of the pulley will cut through 3 magnetic flux fields instead of just one.
also the voltage regulator on a dc gen is far more complicated then it is on a alt, which makes the alternator cheaper, and more efficient, and for a given output, the alternator will alway be smaller than the dynamo thanks to the rotor contruction, so thats why they swapped

Re: Alternator vs Dynamo

Originally Posted by stt

Thanks Lee

so on an old workhorse of a landy theres no real benefit in going to the expense of fitting an alternator, if it aint broke dont fix it!

From what i can remember dynamos used to use a cut Out box which had 3 relays, one establishes an electrical path (switch on contacts) as soon as the Dynmo starts producing a above 12.5Volts and hence couple charging current into the battery and other electrical load, (sorry earlier on I wrote when the ignition was turned on that was incorrect) and then one relay regulates the output current by brifely pulling in when the current exceeded the dynmos rated power, and the 3rd relay pulled in when the voltage reached specified level i.e. approx 14volts, they needed delicate setting and the contacts were spring biased so you could adjust the magnetic pull required for them to trip in on the current and voltage relays.

alternators are controlled electronically, they generate ac voltage, hence why they call them that but the ac output is converted to Dc using a reactifier and a regulator controls the max voltage, but the current is kind of self limiting by its internal windings resitance and windings are chosen so as to tolerate maximum curent flow (power)

Dynmos are sluggish when comapred to alternators as explained by lee303. But it does the job as older cars required less electrical power as in them days (1960s)there weren't any heated windows, air conditioners, and many didn't even have a fan blower for internal ventilation!! nor the radiator cooling fan.

Last edited by MSG; 07-11-2008 at 08:54.
Reason: There was a slightly misconcepted statement now corrected

I am too old for my Calibra and my Calibra is too old for me! we are both stuck!

Re: Alternator vs Dynamo

Above posters have covered it pretty well - dynamos will produce current at a rate roughly proportional to the RPM, alternators approach maximum output much earlier.
Alternators are also much more efficient - take less engine power for comparable output.
Biggest thing you'll have to consider is the electrical draw on the system - standard you should be fine but if you've additional lights, etc, you'll be in trouble very quickly as 'most' dynamos are rated at 25-30 A maximum.
If appeararances are important, there's at least one firm making specially constructed alternators that have the same look and shape as a dynamo - if you're interested, I'll see if I can narrow it down.

Re: Alternator vs Dynamo

gordo,that would be good if you could narrow it down, as the problem i am going to have is that my power steering pump is built onto the back of the dynamo, so if i change the dynamo for an alternator then i need to rethink the power steering pump!

Re: Alternator vs Dynamo

Originally Posted by stt

gordo,that would be good if you could narrow it down, as the problem i am going to have is that my power steering pump is built onto the back of the dynamo, so if i change the dynamo for an alternator then i need to rethink the power steering pump!

Hmm, that is a bugger!
You could try giving these guys a call - have your dynamo converted, perhaps?http://www.racemettleltd.co.uk/dyn.html
Fudge - just noticed this bit "How much do they cost? Prices start from £395.00 including VAT for the C40/L "

was reading a mag' that had the alt -> gen lookalike, if I find it (!) I'll get back to you.
I presume you can't/don't want to gut the dynamo internals and use a separate alternator - room and drive problems?